AGRICULTURAL CHEMISTRY AGROTECHNY. 205 



one yellow variety tested is somewhat lower. Fruits of Dwarf Stone, Truckers 

 Favorite, Red Peach, Yellow Peach, and Yellow Pear, which were picked green 

 and ripened in the incubator at 32 to 33° C. (10 to 22 days), exhibit a higher 

 acid content than either those ripened on the vines or those ripened at the tem- 

 perature of the laboratory. There are considerable differences in the acidity 

 of varieties, but judging from the results of these tests the normally ripened 

 fruits of yellow varieties commonly contain as much acid as those of red 

 vai'leties." 



The tests show no relation between pigmentation and total acidity. 



The nature, value, and limits of biological water analysis, A. Thienemann 

 (Ztschr. Untersuch. Kahr. n. Oenussmtl., 27 (1914), No. 1-3, pp. 273-281).— 

 Biological water analysis is defined as the judgment of the chemical composition 

 of a water on the basis of its fauna and flora. The topics are discussed from 

 various aspects and compared with the results obtained in the chemical exami- 

 nation of water. 



The microscopy of drinking water, G. C. Whipple (Neiv York and London, 

 1914, 3. ed. rewritten and enh, pp. XXI +409, pis. 26, figs. 73).— This is a third 

 and enlarged edition of this work. The first part of the work has been re- 

 written and several new chapters have been added. The most important chap- 

 ters are on the copper treatment of water; the stripping of reservoir sites; the 

 purification of algfe-ladeu waters; and the use of the microscope and photo- 

 micrography (by J. W. M. Bunker). 



Report of committee [of the fertilizer chemistry division] on phosphoric 

 acid, G. Faknham et al. (Jour. Indus, and Engin. Chem., 6 (1914), No. 6, pp. 

 513, 514). — This is a resume of the work done by the committee of the fer- 

 tilizer section of the American Chemical Society since its organization. 



Triammonium citrate, R. A. Hall (Jour. Amer. Chem. Soc, 37 (1915), No. 1, 

 pp. 208-216). — "Triammonium citrate can be obtained readily and easily as a 

 stable compound by the passage of anhydrous ammonia gas into citric acid dis- 

 solved in an anhydrous solvent. The best solvent for this purpose is absolute 

 alcohol heated to its boiling point. The yield of triammonium citrate is quan- 

 titative. Ninety-five per cent alcohol may be used, but the yield is not quan- 

 titative. 



" The salt is a stable, crystalline substance. Analyses show it to have the 

 composition represented by the formula (NH4)3C6H607. It reacts alkaline to 

 rosolic acid. It is exceedingly soluble in water and can not be recrystallized 

 from its water solution. Precipitated, in the cold, from an aqueous solution by 

 addition of alccThol an unstable crystalline form of the salt is obtained. 



" From practical tests in laboratories where daily analyses of fertilizers are 

 made it has been shown that the salt lends itself readily to the making of solu- 

 tions of 1.09 specific gravity at 20° C. ; that this solution of normal ammonium 

 citrate gives, in parallel phosphoric acid determinations, results practically 

 identical with the most carefully prepared ' neutral ' ammonium citrate solu- 

 tions and can, therefoi'e, well be substituted." 



About cholesterol and its estimation in fats, M. Klostebmann and H. 

 Opitz (Ztschr. Untersuch. Nahr. u. GenussmtL, 27 (1914), No. 10, pp. 713- 

 723). — This work was done for the purpose of determining the form in which 

 cholesterol is present in the usual edible fats and the proportions in the free 

 and combined state. 



In solid animal fats (lard, butter, beef tallow, mutton tallow, goose fat, 

 oleomai'garin, and human fat) cholesterol occurs in the free state. In cod liver 

 oil, however, a number of esters are present which contain about one-half of the 

 total cholesterol. 



